As a method for hydrolyzing a fat and/or oil with a fat and/or oil hydrolyzing enzyme such as lipase as a catalyst, there exists a conventional method that is performed by immobilizing an enzyme on a carrier, then allowing it to act on an oil-phase substrate and a water-phase substrate, with the aim of recovery and reuse of the enzyme. Methods for using an immobilized enzyme include the use thereof in a fluidized bed-type reactor (J. Am. Oil Chem. Soc., 72: 1281, 1995), the immobilization of an enzyme on a membrane to form a membrane type reactor (J. Am. Oil Chem. Soc., 62: 1016, 1985), and the packing of an immobilized enzyme, e.g., in a column to form a fixed bed (JP-A-61-85195, JP-A-01-98494, JP-A-05-95792, and JP-A-2000-160188). In the case of the fluidized bed-type reactor, however, there is a problem that the enzyme has not only a short durability but also a prolonged residence time. In the case of the membrane type reactor, on the other hand, there is a problem that the reaction rate is extremely low. Therefore, it has become common to use techniques which involve packing an immobilized enzyme, e.g., in a column to make a fixed bed, through which an oil phase substrate and a water phase substrate are then passed.
Such techniques include a method which is based on the counter current flow of the oil phase substrate and the water phase substrate (JP-A-61-85195, JP-A-01-98494, and JP-A-05-95792) and a method which is based on their concurrent flow (JP-A-2000-160188). The oil phase substrate and the water phase substrate are required to be uniformly mixed in order to effectively proceed with reaction because they are essentially immiscible with each other, and are generally made in the form of an emulsion. Alternatively, there is a method using a liquid-passing rate causing no emulsification because it is difficult for the emulsion particle to reach the enzyme adsorbed within a carrier (JP-A-61-85195).